Variable condenser



l 1, June 7, 1927. G. H. CLARK ,53 360 VARIABLE CONDEISER Filed June 27, I922 4 Jay-1 avwewtoz GEORGE H. CLARK Patented June 7, 1927.

UNITED STATES PA'r QFFICE.

GEORGE H. CLARK, 0F BROOKLYN, NEVI' YORK, ASEBIGNQR T0 RADIO CORPORATIUN OF AMERICA, A CORIPDRATIUN 01" DELAWARE.

VARIABLE GONDENSER.

Application filed June 27, 19252.

This invention relates to electrical condensers and particularly to variable condensers utilized for example for changing the wave length of tuning circuits in radio signalling.

A convenient variable condenser widely used in adjusting radio circuits utilizes spaced rotary, condenser plates mounted on a shaft in combination with similar stationary plates. The stationary and rotary plates are usually semi-circular, although they may, if desired, consist of two 90 sectors diametrically opposite. With semi-circular plates the variation from maximum to minimum requires 180 rotation and with quadrants 90 rotation of the shaft. With this type of condenser it is found that zero capacity is not obtained when the plates are completely in non-opposition and the behavior moreover is not reliable at or near this position, so that the useful capacity range is about 16 to 1. With a fixed inductance this corresponds to a wave length range of 4 to It. This range is not as great as is desirable for many purposes and the object of my invention is to provide a simple arrangement for obtaining a further increase in t e range of capacity and wave length.

In accordance with the invention I pro vide two variable ca acities, one large and the other small, in w ich the minimum capacity of the large ca acity is preferably substantially equal to t e maximum capacity of the smaller capacity. Both capacities may be mounted so as to form a single condenser and the variation of both capacities is controlled by a single adjusting member. In order to give a gradual variation the large condenser is short circuited at minimum capacit and the small condenser is then varied own to its minimum.

The novel features which I believe to be characteristic of 1n invention are particularly set forth in t e appended claims, the invention itself, however, both as to its construction and mode of operation, together with further objects and advantages thereof, will best be-understood by reference to the following description taken in connection with the accompanying drawings in which:

Fig. 1 is a diagrammatic view illustrating a condenser arrangement in accordance with theinvention.

Fig. 2 is a plan view of the short-circuiting arrangement of Fig. 1.

Serial life. 571,249.

Figs. 3 and t are diagrammatic Views of modifications. In these figures the invention is illustrated in connection with rotary condensers as it is especially applicable thereto. Semi-circular plates are utilized although the invention is applicable to the rotary condensers using quadrants or plates of other shape.

lln Fig. 1, two sets of plates 1, 2 are rotatably mounted on the shaft 3, which is adjustable in the usual manner by means of the adjusting knob t carrying a pointer 4 cooperatingwith a dial 4". Two sets of plates 5, 6 cooperate with the rotary sets 1 and 2 respectively. The cooperating plates 1, 5 give the large capacity when opposite each other and the cooperating plates 2, 6 have a maximum capacity when opposite each other substantially eqylial to the minimum capacity of plates 1, 5. hereare numerous arrangements by means of which the combination of the large capacity and the small capacity may be secured and by means of which the I a'dual variation from the maximum of the arge capacity to the minimum of the small capacity may be produced. In the illustration of Fig. l the rotary plates 1 are arranged on diametrically opposite sides of the shaft from the plates 2 which are smaller in size and less in number, although both are preferably semi-circular in shape. The cooperating stationary plates 5 and 6 are on the same side of the shaft and the leading in wires are connected thereto. For short-circuiting one or the other of the condensers a brush 7 is attached to the shaft 3 and con tacts with either of the two semi-circular surfaces 8, 9, which are insulated from each other and connected respectively to the stationary plates 5, 6. By rotating the adjust ing kno through 180' the capacity varies from the maximum of 16 of thelarge condenser to its minimum of 1, bringing the plates 1 over to the right of shaft 3 and the plates 2 over to the left of the shaft. During this period the small condenser has been short-circuited because the stationary and rotary plates 2 and 6 thereof have both been connected to the rin 9. \Vhen the minimum of the large capacity is reached the brush passes oif'of ring 9 on to ring 8, thus removing the short circuit on the small condenser and placing it on the large condenser. The plates 2 and 6 of the small capacity are directly over each other and in the position of maximum capacity. During the next 180 of rotation of knob .4 this capacity decreases in the same ratio as that of the large condenser, that is, in the ratio of 16 to 1. In this manner a range of capacity of 256 to 1 is obtained which corresponds to a wave length range of 16 to 1 with a fixed inductance. ThlS is secured by rotating the condenser knob through 360, although, if desired, the same range may be secured by 180 rotation of the knob by utilizing quadrants instead of semi-circular members.

Substantially the same result is secured by the modification of Fig. 3 which differs from the form described in that the rotating plates 5 of the large condenser cooperate with the stationary plates 5 of the large capacity as well as the stationary plates 6 of the small capacity. The stationary plates are located or? opposite sides of the shaft instead of having the rotating plates on opposite sides.

The modification of Fig. 4 has the stationary plates 5, 6 on opposite sides of the shaft 3 as in Fig. 3 and separate rotatable plates 1, 2 for each capacity, the rotatable plates being located on the same side of the shaft. Two stationary brushes 11, 12 and a rotatable semi circular ring 13 are used instead of one brush and two rings as in Figs. 1' and 3.

Having described my invention, what I claim is:

1. A variable condenser comprising two variable portions, one portion having a maximum capacity substantially equal to the minimum capacity of the other portion and means for short-circuiting thep'ortions in sequence.

2. A variable condenser comprising two variable portions, one portion having a maximum capacity when the other portion has a minimum capacity, a single adjusting means for both portions and means for shortcircuiting each in sequence.

A variable condenser comprising a portion of relatively large maximum capacity and a second portion having a maximum capacity substantially equal to the minimum of the first mentioned portion, and means for successively utilizing said portions includiiig means for short-circuiting the portion not in use.

' 4. A variable condenser comprising a portion of relatively large maximum capacity and a second portion having a maximum capacity substantially equal to the minimum of the first mentioned portion, means for short-circuiting the large portion when at its minimum and the small portion at its maximum and adjusting means for varying both portions and for operating said short-clrcuiting means.

5. A variable condenser comprising a set of rotary and a set of stationary sectors, one of said sets being subdivided into two portions disposed at different positions relative to the cooperating sectors of the other set and means for applying a short-circuiting connection between the sectors of one of said portions and the sectors of the other set.

6. A variable condenser comprising a set of rotary and a set of stationary sectors, one of said sets being subdivided into two portions disposed at different positions relative to the cooperating sectors of the other set and means for successively utilizing said portions.

7. A variable condenser comprising a set of rotary and a set of stationary sectors, one of said sectors being divided into two portions disposed at different positions relative to the cooperating sectors of the other set and adapted to give two capacities such that the maximum of one is substantially equal to the minimum of the other and adjustin members for varying the capacity of boti portions having short circuiting m mberscooperating therewith for short-circ iting the last mentioned portion when adjusted to its minimum value and for short-circuiting the first mentioned portion when adjusted to its maximum value.

8. A variable condenser comprising a set of stationary sectors and a set of rotary sectors, said rotary sectors being divided into two portions at different angular positions proportioned so that the maximum of one is substantially equal to the minimum of the other and positioned so that one reaches its maximum substantially simultaneous with the minimum of the other and means for short-circuiting the larger portion when its minimum is substantially reached and means for short-circuiting the smaller portion when its maximum is substantially reached.

GEORGE H. CLARK. 

